1. Field
The following description relates to an envelope tracking bias circuit.
2. Description of Related Art
In general, a power amplifier (PA) serves to amplify radio frequency (RF) signals in a radio communication band to be transmitted by an antenna. The PA of a portable device, such as a smartphone, typically uses a larger amount of current than other components in the portable device and should satisfy high linearity requirements.
There are various methods for improving PA characteristics. Among such methods, as a method for improving characteristics of amplitude modulation (AM)/AM, AM/phase modulation (PM), and the like of the PA, there is a method for providing an envelope signal of the RF signal applied to the PA to a bias.
A bias voltage in a PA core cell may be provided in a form of sourcing or sinking voltage determined by a circuit structure of a PA integrated circuit (IC), and a magnitude of an envelope tracking (ET) bias provided to an ET core may also be varied depending on an operation and a circuit structure of the PA.
Conventionally, an envelope signal may not be matched to characteristics of the PA because conventional envelope tracking bias circuits provide the envelope signal without considering characteristics of the PA. Thus, the performance suitable for characteristics of the PA may not be exhibited by conventional means.